Aru vs Iru

From WagaWiki

This is a relatively advanced topic. This page will not use romaji and common kanji will not have readings given.

Introduction

The basic rules are

alive = いる / います

not alive = ある / あります

However there is more to it than that.

Moving machines may use います

Moving objects (such as cars or airplanes) may use います even though they are not "alive". This even applies to objects that aren't moving but could start moving at any second (e.g. a parked car with a driver in it).

あります as "existance of people"

Treat the following with caution as it is not an area I am greatly familiar with

It may be rare in modern Japanese but あります can be used in relation to people in a few cases.
See 大辞林

When the existance of somebody is the question in point.

For example

Once upon a time there lived an old couple.
昔々、年をとった夫婦がありました

Where it is clear that the person exists and the location where they exist is in question.

She is now in her sick-bed.
彼女は今病の床にある。

Where the type of environment, position in which they exist is under question.

In all of the above あります cases it is only possible to use あります, it is not the case that います would be a mistake.